9.8. Data Type Formatting Functions

The PostgreSQL formatting functions provide a powerful set of tools for converting various data types (date/time, integer, floating point, numeric) to formatted strings and for converting from formatted strings to specific data types. Table 9-20 lists them. These functions all follow a common calling convention: the first argument is the value to be formatted and the second argument is a template that defines the output or input format.

The to_timestamp function can also take a single double precision argument to convert from Unix epoch to timestamp with time zone. (Integer Unix epochs are implicitly cast to double precision.)

Table 9-20. Formatting Functions

FunctionReturn TypeDescriptionExample
to_char(timestamp, text)textconvert time stamp to stringto_char(current_timestamp, 'HH12:MI:SS')
to_char(interval, text)textconvert interval to stringto_char(interval '15h 2m 12s', 'HH24:MI:SS')
to_char(int, text)textconvert integer to stringto_char(125, '999')
to_char(double precision, text)textconvert real/double precision to stringto_char(125.8::real, '999D9')
to_char(numeric, text)textconvert numeric to stringto_char(-125.8, '999D99S')
to_date(text, text)dateconvert string to dateto_date('05 Dec 2000', 'DD Mon YYYY')
to_timestamp(text, text)timestamp with time zoneconvert string to time stampto_timestamp('05 Dec 2000', 'DD Mon YYYY')
to_timestamp(double precision)timestamp with time zoneconvert UNIX epoch to time stampto_timestamp(200120400)
to_number(text, text)numericconvert string to numericto_number('12,454.8-', '99G999D9S')

In an output template string (for to_char), there are certain patterns that are recognized and replaced with appropriately-formatted data from the value to be formatted. Any text that is not a template pattern is simply copied verbatim. Similarly, in an input template string (for anything but to_char), template patterns identify the parts of the input data string to be looked at and the values to be found there.

Table 9-21 shows the template patterns available for formatting date and time values.

Table 9-21. Template Patterns for Date/Time Formatting

HHhour of day (01-12)
HH12hour of day (01-12)
HH24hour of day (00-23)
MIminute (00-59)
SSsecond (00-59)
MSmillisecond (000-999)
USmicrosecond (000000-999999)
SSSSseconds past midnight (0-86399)
AM or A.M. or PM or P.M.meridian indicator (uppercase)
am or a.m. or pm or p.m.meridian indicator (lowercase)
Y,YYYyear (4 and more digits) with comma
YYYYyear (4 and more digits)
YYYlast 3 digits of year
YYlast 2 digits of year
Ylast digit of year
IYYYISO year (4 and more digits)
IYYlast 3 digits of ISO year
IYlast 2 digits of ISO year
Ilast digits of ISO year
BC or B.C. or AD or A.D.era indicator (uppercase)
bc or b.c. or ad or a.d.era indicator (lowercase)
MONTHfull uppercase month name (blank-padded to 9 chars)
Monthfull mixed-case month name (blank-padded to 9 chars)
monthfull lowercase month name (blank-padded to 9 chars)
MONabbreviated uppercase month name (3 chars)
Monabbreviated mixed-case month name (3 chars)
monabbreviated lowercase month name (3 chars)
MMmonth number (01-12)
DAYfull uppercase day name (blank-padded to 9 chars)
Dayfull mixed-case day name (blank-padded to 9 chars)
dayfull lowercase day name (blank-padded to 9 chars)
DYabbreviated uppercase day name (3 chars)
Dyabbreviated mixed-case day name (3 chars)
dyabbreviated lowercase day name (3 chars)
DDDday of year (001-366)
DDday of month (01-31)
Dday of week (1-7; Sunday is 1)
Wweek of month (1-5) (The first week starts on the first day of the month.)
WWweek number of year (1-53) (The first week starts on the first day of the year.)
IWISO week number of year (The first Thursday of the new year is in week 1.)
CCcentury (2 digits)
JJulian Day (days since January 1, 4712 BC)
RMmonth in Roman numerals (I-XII; I=January) (uppercase)
rmmonth in Roman numerals (i-xii; i=January) (lowercase)
TZtime-zone name (uppercase)
tztime-zone name (lowercase)

Certain modifiers may be applied to any template pattern to alter its behavior. For example, FMMonth is the Month pattern with the FM modifier. Table 9-22 shows the modifier patterns for date/time formatting.

Table 9-22. Template Pattern Modifiers for Date/Time Formatting

FM prefixfill mode (suppress padding blanks and zeroes)FMMonth
TH suffixuppercase ordinal number suffixDDTH
th suffixlowercase ordinal number suffixDDth
FX prefixfixed format global option (see usage notes)FX Month DD Day
SP suffixspell mode (not yet implemented)DDSP

Usage notes for date/time formatting:

Table 9-23 shows the template patterns available for formatting numeric values.

Table 9-23. Template Patterns for Numeric Formatting

9value with the specified number of digits
0value with leading zeros
. (period)decimal point
, (comma)group (thousand) separator
PRnegative value in angle brackets
Ssign anchored to number (uses locale)
Lcurrency symbol (uses locale)
Ddecimal point (uses locale)
Ggroup separator (uses locale)
MIminus sign in specified position (if number < 0)
PLplus sign in specified position (if number > 0)
SGplus/minus sign in specified position
RNroman numeral (input between 1 and 3999)
TH or thordinal number suffix
Vshift specified number of digits (see notes)
EEEEscientific notation (not implemented yet)

Usage notes for numeric formatting:

Table 9-24 shows some examples of the use of the to_char function.

Table 9-24. to_char Examples

to_char(current_timestamp, 'Day, DD  HH12:MI:SS')'Tuesday  , 06  05:39:18'
to_char(current_timestamp, 'FMDay, FMDD  HH12:MI:SS')'Tuesday, 6  05:39:18'
to_char(-0.1, '99.99')'  -.10'
to_char(-0.1, 'FM9.99')'-.1'
to_char(0.1, '0.9')' 0.1'
to_char(12, '9990999.9')'    0012.0'
to_char(12, 'FM9990999.9')'0012.'
to_char(485, '999')' 485'
to_char(-485, '999')'-485'
to_char(485, '9 9 9')' 4 8 5'
to_char(1485, '9,999')' 1,485'
to_char(1485, '9G999')' 1 485'
to_char(148.5, '999.999')' 148.500'
to_char(148.5, 'FM999.999')'148.5'
to_char(148.5, 'FM999.990')'148.500'
to_char(148.5, '999D999')' 148,500'
to_char(3148.5, '9G999D999')' 3 148,500'
to_char(-485, '999S')'485-'
to_char(-485, '999MI')'485-'
to_char(485, '999MI')'485 '
to_char(485, 'FM999MI')'485'
to_char(485, 'PL999')'+485'
to_char(485, 'SG999')'+485'
to_char(-485, 'SG999')'-485'
to_char(-485, '9SG99')'4-85'
to_char(-485, '999PR')'<485>'
to_char(485, 'L999')'DM 485
to_char(485, 'RN')'        CDLXXXV'
to_char(485, 'FMRN')'CDLXXXV'
to_char(5.2, 'FMRN')'V'
to_char(482, '999th')' 482nd'
to_char(485, '"Good number:"999')'Good number: 485'
to_char(485.8, '"Pre:"999" Post:" .999')'Pre: 485 Post: .800'
to_char(12, '99V999')' 12000'
to_char(12.4, '99V999')' 12400'
to_char(12.45, '99V9')' 125'